THE INFLUENZA BACILLUS 145 



flagella have been described by Gordon.) Bacillary 

 forms have been observed in old cultures, and frequently 

 occur in even young cultures. Maynard (Medical Press, 

 November 4, 1914) says this bacillary form grows more 

 rapidly and luxuriantly than the typical micrococcus. 



M. melitensis is of slow growth, especially in the primary 

 cultures from the spleen; on agar in three to four days it 

 forms small semi-transparent droplets, which later become 

 opaque and yellowish -orange in colour. It develops 

 slowly on gelatin as a limited dirty white streak without 

 liquefaction. It does not stain by Gram's method. 

 Inoculated into monkeys, it produces a febrile condition, 

 with enlarged spleen, simulating the human disease; 

 but it is non-virulent to guinea-pigs and rabbits, except 

 on intracerebral inoculation. 



The disease is diagnosed by an agglutination reaction, 

 but dilutions up to 1 in 100 should be prepared, as Hewlett 

 points out that old laboratory strains agglutinate with 

 normal serum in dilution of 1 in 20 or 30. The organism 

 occurs in the blood and milk of goats, and the latter 

 constitutes the main source of infection. Since tli3 

 prohibition of goat's milk to the garrison at Malta (1906) 

 the disease has practically disappeared. The organism 

 is sometimes found in the urine, and less often in the 

 ffeces and milk of patients. It is not apparently a 

 water-borne disease. 



CHAPTER XII 

 The Influenza Bacillus. 



Morphology. Pfeiffer's B. influenza is found in the 

 sputum and nasal secretion during the febrile period of 

 influenza. It is a very small rod, not exceeding 1-5 JJL 

 in length and 0-3 JLC in thickness. It has rounded ends, 

 and is generally found in pairs, but on cultivation grows 

 out into strings. It is Gram-negative. When stained 

 with dilute carbol-fuchsin there is a tendency to bipolar 

 staining. Resistance to outside influences is very 

 slight. 



Cultural Characters. The influenza bacillus is a strict 

 aiTobe. No growth occurs below 25 C., the optimum 



10 



